Generate Code for an Elapsed Time Counter
This example shows a model that includes a triggered subsystem, Amplifier,
consisting of a Discrete-Time Integrator block that uses an elapsed
time counter. The model ex_elapseTime is in the
folder matlab/help/toolbox/rtw/examples.
ex_elapseTime Model
Amplifier Subsystem
Code in the generated header file ex_elapseTime.h for
the model uses 64 bits to implement the timer for the base rate (clockTick0 and clockTickH0).
/*
* Timing:
* The following substructure contains information regarding
* the timing information for the model.
*/
struct {
time_T taskTime0;
uint32_T clockTick0;
uint32_T clockTickH0;
time_T stepSize0;
time_T tFinal;
boolean_T stopRequestedFlag;
} Timing;The code generator allocates storage for the previous-time value
and elapsed-time value of the Amplifier subsystem
(Amplifier_PREV_T) in the D_Work(states) structure
in ex_elapsedTime.h.
/* Block states (auto storage) for system '<Root>' */
typedef struct {
real_T DiscreteTimeIntegrator_DSTATE;
/* '<S1>/Discrete-Time Integrator' */
int32_T clockTickCounter;
/* '<Root>/Pulse Generator' */
uint32_T Amplifier_ELAPS_T[2];
/* '<Root>/Amplifier' */
uint32_T Amplifier_PREV_T[2];
/* '<Root>/Amplifier' */
} DW_ex_elapseTime_T;The elapsed time computation is performed as follows within
the ex_elapseTime_step function:
/* ---
Outputs for Triggered SubSystem:
'<Root>/Amplifier' incorporates:
TriggerPort: '<S1>/Trigger'
--- */
zcEvent = rt_ZCFcn(RISING_ZERO_CROSSING,
&ex_elapseTime_PrevZCX.Amplifier_Trig_ZCE,
((real_T)rtb_PulseGenerator));
if (zcEvent != NO_ZCEVENT) {
elapseT_H = ex_elapseTime_M->Timing.clockTickH0 -
ex_elapseTime_DW.Amplifier_PREV_T[1];
if (ex_elapseTime_DW.Amplifier_PREV_T[0] >
ex_elapseTime_M->Timing.clockTick0) {
elapseT_H--;
}
ex_elapseTime_DW.Amplifier_ELAPS_T[0] =
ex_elapseTime_M->Timing.clockTick0
- ex_elapseTime_DW.Amplifier_PREV_T[0];
ex_elapseTime_DW.Amplifier_PREV_T[0] =
ex_elapseTime_M->Timing.clockTick0;
ex_elapseTime_DW.Amplifier_ELAPS_T[1] =
elapseT_H;
ex_elapseTime_DW.Amplifier_PREV_T[1] =
ex_elapseTime_M->Timing.clockTickH0;
As shown above, the elapsed time is maintained as a state of the triggered subsystem. The Discrete-Time Integrator block finally performs its output and update computations using the elapsed time.
/* ---
DiscreteIntegrator: '<S1>/Discrete-Time Integrator'
--- */
OUTPUT = ex_elapseTime_DW.DiscreteTimeIntegrator_DSTATE;
/* ---
Update for DiscreteIntegrator:
'<S1>/Discrete-Time Integrator' incorporates:
Constant: '<Root>/Constant'
--- */
ex_elapseTime_DW.DiscreteTimeIntegrator_DSTATE += 0.3 * (real_T)
ex_elapseTime_DW.Amplifier_ELAPS_T[0] * 1.5;